Codes

I have a 1997 Pontiac Sunfire with a 2.2 litre engine and an automatic transmission,and it has 101,000 on it as of right now..The problem is my check engine light came on and it stays on continuously...I took a Scanner and read the codes just a little while ago and it is reading out 4 different codes and I was wanting to see if anyone can tell me what these codes mean?? The code numbers are:::P0121 P0341 P0420 and P0335...if anyone out there can tell me what these codes mean I would surely appreciate it......

po121 is throttle/pedal position sensor/switch a circuit range/ performance problem

po335 is crankshaft position sensor A circuit malfunction

po341 is camshaft position sensor circuit range/performance

po420 is catalyst system efficiency below threshold (bank 1)

Hope that helps those are all the OBDII generic codes.